More than 100 militants armed with rocket-propelled grenades and guns launched the attack in Nari district of Kunar province, attacking the post from three directions before dawn.
"The attackers were heavily armed," a senior police officer in Nari district, who declined to be named, told AFP. "We have recovered the bodies of 13 of our soldiers, the outpost has been nearly destroyed."
The attack was finally pushed back after several hours when Afghan military and police reinforcements arrived. One soldier was severely injured, police said.
Defence ministry spokesman General Mohammad Zaher Azimi confirmed the attack but said that exact casualty figures were not available.
"We are still in the process of gathering information," he said.
Taliban spokesman Zabiullah Mujahid claimed responsibility for the assault in an email to AFP and said that the militants had seized all weapons and ammunition from the army post.
The border region between Afghanistan and Pakistan is a key battleground in the fight against the militants, many of whom use safe havens inside Pakistan to launch attacks against Afghan soldiers and the US-led military coalition.
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